Modulation of protein glutaminase α-helix and disulfide bonds in a sunflower pollen microgel microenvironment: A strategy to enhance enzyme activity and stability

Protein glutaminase (PGase) can improve plant protein solubility, but its activity tends to decline under the influence of external factors. Here, we developed a novel PGase-stabilizing agent (sunflower pollen microgel, SPMG) and investigated the mechanism for its stabilizing effect on PGase. Alkali treatment could regulate the physicochemical microenvironment of SPMG, and its ability to stabilize PGase declined with prolonged treatment time. SPMG increased PGase activity by a maximum of 49.24 %, while enhanced its storage stability by 30.61 %, 21.64 %, and 26.00 % at 4 °C, 25 °C, and 37 °C, respectively. SPMG improved PGase properties through hydrophobic interaction, resulting in the burying of inner hydrophobic groups and enhancement of intermolecular hydrogen bonding, which promoted the α-helix content from 23.28 % to 26.19 %. Additionally, these interactions facilitated the sulfhydryl-disulfide bond exchange reaction between PGase molecules, significantly increasing the disulfide bond content by nearly 80 %. This compact structure ultimately enhanced the activity and stability of PGase.